U.S. patent number 4,187,092 [Application Number 05/906,089] was granted by the patent office on 1980-02-05 for method and apparatus for providing increased thermal conductivity and heat capacity to a pressure vessel containing a hydride-forming metal material.
This patent grant is currently assigned to Billings Energy Corporation. Invention is credited to Ronald L. Woolley.
United States Patent |
4,187,092 |
Woolley |
February 5, 1980 |
Method and apparatus for providing increased thermal conductivity
and heat capacity to a pressure vessel containing a hydride-forming
metal material
Abstract
A method and apparatus are disclosed for providing increased
thermal conductivity and heat capacity to a pressure vessel
containing a hydride-forming metal material which is capable of
absorbing and storing relatively large amounts of hydrogen gas. An
elongate pressure vessel, having an opening therein for charging
and discharging hydrogen therefrom and valve means in combination
with the opening for controlling flow of hydrogen gas to and from
the container, is provided with a plurality of elongate, aluminum
magnesium, or copper tubes as a tube bundle, with the longitudinal
axis of the tubes being parallel to the longitudinal axis of the
vessel. The tubes are packed in the vessel so that tubes are in
firm contact with adjacent tubes, and the outer tubes of the bundle
are in firm contact with the longitudinal inside surfaces of the
vessel as well as with adjacent tubes in the bundle. Particulate,
hydride-forming, metal material substantially fills the otherwise
void spaces within the tube-containing vessel. Thermal conductivity
and thermal capacity of the bed of particulate material in the
tube-containing vessels are increased by as much as 240% and 15%,
respectively, in comparison to equivalent size beds of the same
particulate material in non-tube containing vessels. An existing
pressure vessel can be retrofitted with thetightly packed tubes by
cutting tubes, having an outside diameter smaller than the valve
opening in the pressure vessel, to lengths having a longitudinal
dimension shorter than the longitudinal dimension of the pressure
vessel. The lengths of tubes are inserted, one at a time, into the
pressure vessel through the valve opening therein, and the inserted
tubes are organized into the tightly packed tube bundle.
Inventors: |
Woolley; Ronald L. (Orem,
UT) |
Assignee: |
Billings Energy Corporation
(Provo, UT)
|
Family
ID: |
25421912 |
Appl.
No.: |
05/906,089 |
Filed: |
May 15, 1978 |
Current U.S.
Class: |
62/46.2; 423/248;
34/416 |
Current CPC
Class: |
F17C
11/005 (20130101); C01B 3/0005 (20130101); Y02E
60/327 (20130101); Y02E 60/321 (20130101); Y02E
60/32 (20130101) |
Current International
Class: |
F17C
11/00 (20060101); C01B 3/00 (20060101); F17C
011/00 () |
Field of
Search: |
;62/48 ;34/15 ;423/248
;123/DIG.12 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Capossela; Ronald C.
Attorney, Agent or Firm: Thorpe; Calvin E.
Claims
I claim:
1. A hydrogen storage system comprising:
an elongate pressure vessel having an opening therein for charging
hydrogen to the vessel and for withdrawing hydrogen from the
vessel;
valve means in combination with the opening in said vessel for
controlling the flow of hydrogen gas to and from said vessel;
a plurality of elongate tubes being made of a metal selected from
the group consisting of aluminum, magnesium, and copper, and being
positioned within said pressure vessel with the longitudinal axes
of said tubes being parallel to the longitudinal axis of said
vessel, each of said tubes being in firm contact along its
longitudinal surface with the longitudinal surfaces of at least
three other tubes to form a coherent, tightly packed tube bundle in
which the outer tubes thereof also make firm contact along their
longitudinal surfaces with the longitudinal inside surface of said
vessel; and
particulate, hydride-forming, metal material substantially filling
the otherwise void spaces within said vessel, said metal material
being capable of reacting with and absorbing hydrogen gas at a
given temperature and pressure and thereafter releasing the
hydrogen gas when the pressure on the hydrogen-containing material
is reduced and/or the temperature of the hydrogen-containing
material is increased.
2. A hydrogen storage system in accordance with claim 1, wherein
each of the tubes is provided with a plurality of spaced apart
notches in the longitudinal sides thereof to facilitate filling of
the hollow interiors of the tubes and spaces between tubes with
said particulate, metal material.
3. A hydrogen storage system in accordance with claim 1, wherein
said particulate, metal material is a metal alloy comprising at
least two elements selected from the group consisting of iron,
titanium, nickel, calcium, magnesium, manganese, and rare earth
elements.
4. A hydrogen storage system in accordance with claim 3, wherein
said particulate, metal material comprises an alloy selected from
the group consisting of iron-titanium alloys, lanthanum-nickel
alloys, calcium-nickel alloys, mischmetal-nickel alloys, manganese
nickel alloys, and mischmetal-calcium-nickel alloys.
5. A method of increasing the thermal conductivity and heat
capacity of a pressure vessel containing a bed of particulate,
hydride-forming, metal material, said method comprising:
preparing lengths of tubes which are made of a metal selected from
the group consisting of aluminum, magnesium, and copper, said tubes
having a longitudinal dimension shorter than the longitudinal
dimension of the pressure vessel, with said tubes also having an
outside diameter smaller than the valve opening in the pressure
vessel;
inserting the lengths of tubes into the pressure vessel through the
valve opening therein,
organizing the tubes which are inserted into said pressure vessel
to form a tightly packed tube bundle in which adjacent tubes are in
firm contact along the longitudinal surfaces thereof, with the
outer tubes of said bundle also making firm contact along their
longitudinal surfaces with the longitudinal, inside surface of said
vessel; and
substantially filling the otherwise void spaces in the vessel with
a particulate, hydride-forming, metal material which is capable of
reacting with and absorbing hydrogen gas at a given temperature and
pressure and thereafter releasing the hydrogen gas when the
pressure on the hydrogen-containing material is reduced and/or the
temperature of the hydrogen-containing material is increased.
6. A method in accordance with claim 5, wherein the tube bundle is
forced into a tightly packed configuration by inserting a series of
tubes of various outside diameters into said vessel with the
largest tubes having a diameter just small enough to pass through
the valve opening, said largest tubes being inserted into said
vessel first, followed by the next smaller tubes in order of their
size, with the last tubes being forced into said vessel to compress
and tighten the tube bundle therein.
7. A method in accordance with claim 6, wherein the tube bundle is
forced into even tighter packed configuration by forcing solid rods
thereinto between tubes subsequent to the installation of all the
tubes.
Description
BACKGROUND OF THE INVENTION
1. Field
This invention pertains to the storage of hydrogen in the form of
solid metal hydrides contained in appropriate containers, e.g.,
pressure vessels. In particular, the invention relates to methods
and apparatus for increasing the thermal conductivity and thermal
capacity of the bed of particulate metal hydrides contained in the
storage containers.
2. State of the Art
One factor that has limited the use of hydrogen, especially as a
fuel, is the difficulty of efficiently and safely storing it.
Storage as a liquid is costly due to the energy expended in
liquifying the hydrogen, and the extremely low temperature of the
liquid hydrogen presents numerous safety problems. Storing hydrogen
as a gas requires extremely heavy and bulky containers and is
impractical for many contemplated uses of hydrogen.
An attractive alternative to the conventional storage methods has
been recently proposed in which hydrogen is stored in the form of a
metallic hydride. Many metals and alloys will reversibly react with
hydrogen to form metallic hydride which contain more hydrogen per
unit volume than liquid hydrogen. Heat is liberated when the
hydrogen and metallic material reacts to form the hydrides and must
be removed to allow the hydriding reactions to proceed to
completion. Conversely, heat is absorbed during the decomposition
of the hydride to release hydrogen, and the hydrides are preferably
heated during their decomposition to provide an adequate rate of
liberatation of hydrogen therefrom.
Heating and cooling of the metallic hydride material has been
accomplished by conventional techniques including heating or
cooling the container in which the material is held, or spacing
tubes throughout the bed of hydride material and circulating a heat
exchange medium in the tubes. In such techniques, the amount of
heat transferred to the metallic hydride depend on the conductive
heat transfer characteristics of the particulate, metal material.
Unfortunately, particulate, metal hydride materials are poor
conductors of heat. The rather low thermal conductivities of beds
of such material imposes severe limitations on the design of such
storage containers.
OBJECTIVES
The primary objective of the present invention was to provide a
method and apparatus for increasing the thermal conductivity of
beds of particulate, metal hydride materials contained in pressure
vessels, and in particular to modifying existing pressure vessels
so as to achieve the increase in thermal conductivity without
effecting the certification of such vessels. Another objective was
to provide for increased thermal capacity of the beds of metal
hydride contained in the pressure vessels.
SUMMARY OF THE INVENTION
The above objectives are achieved, in accordance with the present
invention, by providing a hydrogen storage system comprising an
elongate pressure vessel containing a plurality of aluminum,
magnesium, or copper tubes positioned therein to form a coherent,
tightly packed, tube bundle in which the outer tubes thereof also
make firm contact with the inside surface of the vessel.
Particulate, hydride-forming metal material substantially fills the
otherwise void spaces within the tube-containing vessel.
The tube-containing vessel is advantageously made from an existing
certified pressure vessel in which the tubes are retrofitted.
Throughout the specification, the term "certified pressure vessel"
and "certification" refer to vessels which have been constructed
and tested in accordance with a particular code as established by a
regulatory agency, such as state or federal agencies, or A.S.M.E.,
etc. In retrofitting an existing, certified vessel, the valve means
is removed from the opening in the vessel, and aluminum, magnesium,
or copper tubes, having an outside diameter smaller than the
opening in the vessel, are cut into lengths which are at least
slightly shorter than the longitudinal dimension of the vessel. The
tubes are inserted, one at a time, into the vessel through the
opening therein. The tubes are arranged arranged into a tube
bundle, with the longitudinal axis of each tube in the bundle being
parallel to the longitudinal axis of the vessel. The tubes are
forced into the vessel to form a firmly packed tube bundle in which
each tube is in firm contact along its longitudinal surface with
the longitudinal surfaces of at least three other tubes, and in
which the outer tubes also make firm contact along their
longitudinal surfaces with the longitudinal inside surface of the
vessel.
The void spaces remaining in the vessel following the installation
of the tube bundle therein is subsequently substantially filled
with particulate, hydride-forming metal material, and the valve
means is then replaced in the opening of the vessel. The
hydride-forming metal material is a metal or metal alloy which is
capable of reacting with and absorbing hydrogen gas at a given
temperature and pressure and thereafter releasing the hydrogen gas
when the pressure is reduced and/or the temperature of the material
is increased, i.e., hydrogen is absorbed when the partial pressure
of hydrogen is greater than the equilibrium pressure associated
with the hydride forming metal material and is released when the
partial pressure of hydrogen is less than the equilibrium pressure
associated with such material. Preferably, the metal hydride is an
alloy comprising at least two elements selected from the group
consisting of iron, titanium, nickel, calcium, magnesium,
manganese, and rare earth elements. Particularly advantageous
alloys include iron-titanium alloys, lanthanum-nickel alloys,
calcium-nickel alloys, mishmetal-nickel alloys, manganese-nickel
alloys, and mischmetal-calcium-nickel alloys. Mischmetal is the
common name given to a mixture of rare earth elements.
Thermal conductivity and thermal capacity of the bed of
hydride-forming material in the vessel of the present invention are
increased by as much as or more than 240% and 15%, respectively, in
comparison to equivalent size beds of the same particulate material
in conventional, non-tube containing vessels.
THE DRAWINGS
A particular embodiment of the present invention representing the
best mode presently contemplated of carrying out the invention is
illustrated in the accompanying drawings, in which:
FIG. 1 is perspective view of a pressure vessel in accordance with
the invention, with the side wall of the vessel being broken away
to show the tube bundle therein;
FIG. 2 is a cross sectional view taken on line 2--2 of FIG. 1;
and
FIG. 3 is a partial perspective of a vessel similar to the one
shown in FIG. 1, showing one of the last tubes to be forced into
the tube bundle through the valve opening of the vessel.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
As illustrated in FIGS. 1-3, a plurality of tubes 10 are positioned
within a pressure vessel 11 to form a coherent, tightly packed
bundle, wherein the longitudinal axes of the tubes 10 are parallel
to the longitudinal axis of the vessel 11. The tubes are preferably
thin walled and made of aluminum, copper, or magnesium to avoid any
problem with interaction between the tubes and the hydrogen
atmosphere within the vessel 11. The vessel 11 can be made of
aluminum, copper, stainless steel, carbon steel, and other metals
when properly designed in accordance with known technology (see
Hydrogen-Environment Embrittlement of Metals, a NASA Technology
Survey by Robert P. Jewett, Robert J. Walter, Willis T. Chandler,
and Richard P. Frohmberg, NASA Tech Brief B73-10168, June
1973).
The tubes 10 are packed firmly into a bundle within the vessel 10
so that each tube in the bundle is in firm contact along its
longitudinal surface with the longitudinal surfaces of at least
three other tubes. In addition, the outer tubes in the bundle make
firm contact along their longitudinal surfaces with the
longitudinal inside surface of said vessel.
The otherwise void spaces remaining in the vessel 11 containing the
tubes 10 is substantially filled with a particulate,
hydride-forming, metal material 12 (see FIG. 2). The metal material
12 is capable of reacting with and absorbing hydrogen gas under
conditions in which the hydrogen gas in the vessel 11 has a partial
pressure greater than the equilibrium pressure of the material 12
and of subsequently releasing hydrogen gas when the partial
pressure of hydrogen in the vessel 11 is less than the equilibrium
pressure of the metal material 12. The equilibrium pressure of the
metal material 12 can be increased by heating the material 12, and,
of course, lowering of pressure in the vessel below the equilibrium
pressure results in the release of hydrogen from the metal material
12.
To facilitate filling of the otherwise void spaces with metal
material 12, a plurality of spaced apart notches 13 (see FIG. 3)
are provided in the longitudinal sides of each of the tubes 10. The
notches 13 are arranged randomly around each tube to provide a
plurality of access openings to the interior of each tube 10. The
notches 13 allow particulate material 12 to flow to and from the
interior of the tubes 10 and the spaces between tubes, thereby
facilitating the filling of the void spaces with the particulate
material 12.
A conventional pressure valve 14 is connected to the valve opening
to control inflow and outflow of hydrogen gas from the vessel
11.
The tubes 10 can be positioned within the vessel 11 during the
manufacture of the vessel 11, or, as will be further explained
hereinafter, the tubes can be retrofitted in an existing pressure
vessel 11. If positioned in the vessel 11 during the construction
of the vessel, the tubes 10 are inserted through the open end of
the vessel prior to the rolling down of that end to form the valve
opening therein. This entails having the full bundle of tubes 10 in
the vessel 11 during the rolling and forming of the valve
opening.
It is advantageous to retrofit the tubes 10 into a completely
formed pressure vessel, thus avoiding interposing the step of
inserting the tubes 10 into the vessel during the manufacturing of
the vessel.
Tubes 10 are readily inserted into the vessel 11 through the valve
opening 15 (see FIG. 3). The tubes 10 made of aluminum, magnesium,
or copper are cut to lengths having a longitudinal dimension
shorter than the longitudinal dimension of the pressure vessel 11.
The lengths of tubes 10 are then inserted one at a time into the
pressure vessel 11 through the valve opening 15 therein.
The tubes 10 are organized into a tightly packed tube bundle as
best illustrated in FIG. 2. Adjacent tubes 10 are in firm contact
along the longitudinal sides thereof, and the outer tubes 10 of the
bundle also make firm contact along their longitudinal surfaces
with the longitudinal, inside surface of the vessel 11. To achieve
optimum packing of the tubes 10 into the tube bundle, the initial
tubes which are insulated into the vessel 11 have an outside
diameter just smaller than the valve opening 15 in the pressure
vessel. These tubes are positioned substantially around the
interior surface of the vessel (see FIG. 2). Tubes having smaller
outside diameters are then inserted into the vessel to form the
next course of tubes, with each course of tubes being slightly
smaller than the previous course. By utilizing such a procedure, a
tightly packed tube bundle can be achieved in which the packing of
the outer tubes closely approaches being hexagonal, and the tubes
near the center of the bundle contact at least five adjacent tubes.
The last several tubes, i.e. the last two or three, forced into the
tube bundle to compress the tube bundle as much as possible. In
addition, several solid rods 16 (FIG. 2) of appropriate diameter
are advantageously forced into the center part of the tube bundle
after all the tubes which can feasibly be forced into the bundle
have been inserted. The rods 16 further compress the tubes in the
tube bundle so that optimum contact is achieved between adjacent
tubes in the bundle.
Following installation of the tubes 10 in the pressure vessel 11,
the particulate, hydride-forming metal material 12 is introduced
into the vessel 11 through the valve opening 15. Sufficient
particulate material 12 is added to the vessel 11 to substantially
fill the otherwise void spaces therein, i.e., the volume within the
tubes and the spaces between adjacent tubes.
Whereas this invention is described with respect to particular
embodiments, it is to be understood that changes may be made
therein and other embodiments constructed without departing from
the novel inventive concepts set forth herein and in the claims
which follow.
* * * * *